Final figures on the minimum temperature between dusk on Wednesday and dawn yesterday were not available last night, but hourly temperature readings from Christchurch Airport show the thermometer hovered between 24 and 26 degrees Celsius for much of Wednesday night.

A blob of extremely warm air from the Australian outback crossed the South Island overnight on Wednesday and intensified as a result of the foehn effect.

The dry gusty nor'west winds heated up as they descended on the Canterbury side of the ranges.

National Institute of Water and Atmospheric Research principal climate scientist Brett Mullan said the previous highest overnight minimums for the city were 22.6C on February 7, 1970, 22.4C on January 14, 1988 and 21.3C on January 7, 1991.